Magnetic separation of metals-contaminated equlibrium catalyst (ECat) from ECat particles having a lower metal content was recently commercialized. Aspects of this process are disclosed in one or more of U.S. Pat. No. 4,406,773 to Hettinger, Jr. et al.; U.S. Pat. No. Re. 35,046 to Hettinger, Jr. et al.; U.S. Pat. No. 5,147,527 to Hettinger, Jr. et al.; U.S. Pat. No. 5,171,424 to Hettinger; U.S. Pat. No. 5,190,635 to Hettinger; U.S. Pat. No. 5,198,098 to Hettinger, Jr.; U.S. Pat. No. 5,230,869 to Hettinger et al.; U.S Pat. No. 5,328,594 to Hettinger; U.S. Pat. No. 5,364,827 to Hettinger et al.; U.S. Pat. No. 5,393,412 to Hettinger; and U.S. Pat. No. 5,538,624 to Hettinger; all of which are hereby incorporated by reference.
Some other work has been done in the area of magnetic separation of FCC catalyst. U.S. Pat. No. 5,250,482, to Doctor, used a super-cooled, quadrupole open-gradient magnetic separation system to separate ECat having more than about 2000 ppm nickel equivalents from ECat having less about 2000 ppm nickel equivalents. The patentee reported an anomaly, namely that the relatively low-metal catalyst "that is the material having less than about 2000 ppm nickel equivalent . . . " was not as active as the higher metal catalyst. The differences reported in metals levels were not large. Low susceptibility catalyst had 2022 ppm nickel equivalents while high susceptibility catalyst had 2261 nickel equivalents ppm. The patentee taught sending the low susceptibility material to a reducing zone, and from there back to the FCC reactor. The teachings of the '482 patent can be summarized as follows:
(1) use the Hettinger magnetic separation process to remove at least the highest metal-containing material (10,000 ppm plus nickel equivalents); PA1 (2) separate the remaining catalyst into a 2000-6000 ppm fraction and a 2000 minus ppm nickel equivalents fraction; PA1 (3) recycle the 2000-6000 ppm material directly to the FCC process; PA1 (4) treat the 2000 minus nickel equivalent material to enhance catalytic activity and recycle the treated material to the reactor. PA1 a) mixing a metals-contaminated, crackable hydrocarbon feed with a source of hot regenerated catalyst in a cracking reaction zone of an FCC unit to produce a mixture of cracked products and spent catalyst containing metals deposited on the catalyst during the cracking reaction; PA1 b) separating the spent catalyst from the cracked products; PA1 c) removing the cracked products from the FCC process; PA1 d) stripping the spent catalyst in a catalyst stripping zone by contact with stripping vapor to remove strippable hydrocarbons from the spent catalyst and produce stripped catalyst; PA1 e) regenerating the stripped catalyst at catalyst regeneration conditions by contact with oxygen or an oxygen-containing gas to produce regenerated, metals-contaminated catalyst which is recycled to the cracking reaction zone; PA1 f) recirculating the catalyst through steps (a) through (e) for an average residence time effective to build up a magnetic metals content in active catalyst particles so that a majority of the active catalyst has an intermediate to low magnetic metals content; PA1 g) at least periodically removing a fraction of catalyst particles from the FCC unit and replacing the removed fraction with catalyst comprising a majority of catalytically active particles and a minority of relatively inert particles having less than 1/10th the cracking activity of the active catalyst; and PA1 h) magnetically separating the removed fraction into:
There remains a need in the art for a better way of processing or retaining the active catalyst from the 2000 minus nickel fraction, and/or for recovering the active catalyst from the 2000 minus nickel fraction with the 2000-6000 ppm nickel fraction. As far as applicants are aware, there is no teaching or suggestion in the prior art of a process which tags the active catalyst so that most of it is retained in the 2000-6000 ppm nickel fraction, leaving mainly inactive particles in the 2000 ppm minus nickel fraction.